1. Field of the Invention
The present invention belongs to the technical field of film image reading that is utilized for digital photo-printers and the like and, more specifically, the present invention relates to an interpolation arithmetic method that is preferably utilized in reading images using an area image sensor in which reading elements are arranged in a hound""s tooth check form, and to an image reader that uses the area image sensor.
2. Description of the Related Art
Heretofore, images recorded on photographic films such as negative and reversal films (which are hereunder referred to simply as xe2x80x9cfilmsxe2x80x9d) have been commonly printed on light-sensitive materials (photographic paper) by means of direct exposure in which the film images are projected onto the light-sensitive materials.
On the other hand, in recent years, a printing apparatus which utilizes digital exposure, that is, a digital photo-printer, has been put to practical use which photoelectrically reads an image recorded on a film, converts the read image to a digital signal and then to image data for recording purposes by applying various kinds of image processing, scans to expose a photosensitive material by recording light modulated according to the image data to record an image (a latent image), and has a (finished) print.
The digital photo-printer is basically composed of a scanner for photoelectrically reading an image recorded on a film (an image reader), an image processing apparatus for applying predetermined processing on image data read by the scanner or image data supplied by a digital camera or the like to have image data for image recording, i.e., exposure conditions, a printer for recording a latent image by scanning to expose a photosensitive material by, for example, an optical beam scanning (an image recording apparatus), and a processor for applying development processing on the photosensitive material exposed by the printer to have a (finished) print on which the image is reproduced (an developing apparatus).
According to such a digital photo-printer, since an image is processed as digital image data, not only an image photographed on a film but also an image photographed by a digital camera or the like and an image obtained by communication network such as the Internet can be outputted as a print.
In addition, since image processing (optimization) can be performed by image data processing, a high-definition print can be obtained which was unavailable with a conventional direct exposure by preferably performing gradation adjustment, color balance adjustment, color/density adjustment, and the like.
A scanner (including various kinds of film scanners) provided in the digital photo-printer of this kind, for example, makes reading light incident on a film (its one image=one frame) to acquire projected light that carries the image, images the projected light on an area image sensor such as an area CCD sensor, and photoelectrically reads the image. By reading the image step by step using reading light of R (red), G (green) and B (blue), the image photographed on the film is resolved to three primary colors, R, G and B, and is photoelectrically read.
Here, in the scanner using such an area CCD sensor, an image is usually read using an area CCD sensor in which reading elements are arranged in a square check form or square form (usually arranged in the longitudinal direction and latitudinal direction of the film).
On the other hand, in recent years, an area CCD sensor in which reading elements are arranged in a hound""s tooth check form has been realized, which is used in a digital camera and the like.
With the area CCD sensor in which reading elements are arranged in a hound""s tooth check form, since the reading elements can be arranged more densely compared with the conventional CCD sensor having the square check form arrangement of reading elements, area efficiency of a receiving section can be made extremely high. As a result, higher sensitivity, more reduced noise (improved S/N ratio), wider dynamic range, or the like can be attained compared with the conventional area CCD sensor having the square check form arrangement of reading elements.
In addition, the area CCD sensor in which reading elements are arranged in a hound""s tooth check form also has an advantage that a larger number of effective pixels can be obtained with a number of pixels identical with those in the one having the square check form arrangement of reading elements.
As described above, the area CCD sensor in which reading elements are arranged in a hound""s tooth check form has many advantages compared with the one having the square check form arrangement of reading elements.
However, a (film) scanner making full use of such excellent characteristics has not been realized yet.
The present invention has been devised in view of the above and other drawbacks, and it is an object of the present invention to provide an interpolation arithmetic method and an image reader (a film scanner) that are capable of, when reading a film image using an area CCD sensor in which reading elements are arranged in a hound""s tooth check form, making full use of excellent characteristics of the area CCD sensor.
According to the present invention, an image can be read with high accuracy, and an output of a high-resolution image with less artifacts is available by making full use of the excellent characteristics of the above-mentioned area CCD sensor having the hound""s tooth check form arrangement of reading elements.
In order to attain the object described above, the present invention provides an interpolation arithmetic method comprising the steps of performing allocation of second image signals by interpolating first image signals of neighboring two or more reading elements outputted from an area image sensor in which the reading elements are arranged in a hound""s tooth check form; and rearranging the second image signals or the first and second image signals in a square check form from the first image signals outputted from the reading elements of the area image sensor.
Preferably, the first image signals of the neighboring two or more reading elements are those of two reading elements closest to each other.
Preferably, the first image signals of the neighboring two or more reading elements are those of neighboring four reading elements.
Preferably, the first image signals of the neighboring two or more reading elements are those of neighboring sixteen reading elements.
Preferably, the allocation of a second image signal is performed in a position between the interpolated reading elements.
Preferably, the allocation of a second image signal is performed in a midpoint between the interpolated reading elements.
In order to attain the object described above, the present invention provides an image reader comprising a light source section for emitting reading light incident on a film held in a predetermined reading position; an area image sensor in which reading elements are arranged in a hound""s tooth check form; an imaging optical system for imaging on the area image sensor projected light which carries an image photographed on the film and which is obtained by making the reading light incident on the film; and at least one of a pixel shifting device of the area image sensor, and an interpolation arithmetic section for rearranging second image signals of pixels by interpolating first image signals outputted from the respective reading elements of the area image sensor.
Preferably, the image reader comprises both of the pixel shifting device and the interpolation arithmetic section, a reading mode for performing only pixel shifting, a reading mode for performing only rearrangement of the second image signals of the pixels and a reading mode for performing both of the pixel shifting and the rearrangement of the second image signals of the pixels are provided, and one of the reading modes and a number of times of the pixel shifting are selected in accordance with a resolution designated for image reading and a magnification of an output.
Preferably, the interpolation arithmetic section uses an interpolation arithmetic method comprising the steps of performing allocation of second image signals by interpolating first image signals of neighboring two or more reading elements outputted from an area image sensor in which the reading elements are arranged in a hound""s tooth check form and rearranging the second image signals or the first and second image signals in a square check form from the first image signals outputted from the reading elements of the area image sensor.
Preferably, the first image signals of the neighboring two or more reading elements are those of two reading elements closest to each other.
Preferably, the first image signals of the neighboring two or more reading elements are those of neighboring four reading elements.
Preferably, the first image signals of the neighboring two or more reading elements are those of neighboring sixteen reading elements.
Preferably, the allocation of a second image signal is performed in a position between the interpolated reading elements.
Preferably, the allocation of a second image signal is performed in a midpoint between the interpolated reading elements.